BIO 3303 Lecture Notes - Lecture 12: Chromophore, Signal Transduction, Opsin
30 Aug 2016
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Document Summary
Photoreceptors: transduce energy from photons into changes in membrane potential: photopigment (protein with chromophore) changes conformation when absorbs light, activates signal transduction cascade leading to graded changes in membrane potential and nt release. Photoreceptive organs: structures specialized for light detection, encode direction, intensity of light, and contrasts, diversity of photoreceptive organs. Photopigment when it changes shape causes changes in membrane and nt release all of that is happening inside a fully developed photoreceptive organ. Photoreceptors respond to a small portion of electromagnetic spectrum (300-1000nm: visible spectrum (humans): 350-750nm, variable in other species. Photoreceptors evolved in aquatic ancestors: light attenuates in water, only some wavelengths penetrate into water column. Visible spectrum is not lost in water visible light can penetrate in the water tells us that our eyeballs evolved under water. Because they"re so carefully selected to allow visible spectrum to go through the water. Rhabdomeric photoreceptors: apical surface contains photopigments in microvillar projections.
